Rheological investigations of ultrafine galena particle slurries under flotation-related conditions

The rheological behaviour (viscosities and extrapolated yield values) of ultrafine galena particle slurries under flotation-related conditions has been studied using a concentric cylinder rheometer. The influence of pulp density, pH and ethyl xanthate concentration is reported. The observed aggregation phenomena are discussed with respect to galena surface chemistry as probed by electrokinetic studies, microflotation and X-ray photoelectron spectroscopy. At greater than 50% solid contents non-Newtonian rheological behaviour is evident, with high yield values and shear thinning properties indicative of pulp aggregation. Under mildly alkaline conditions, galena slurry rheology is controlled by repulsive electrostatic forces, with a high level of galena particle dispersion, whereas under mildly acidic conditions the rheology is significantly influenced by hydrophobic interactions. The introduction of galena particle hydrophobicity through ethyl xanthate addition results in enhanced galena particle attraction and increased floatabilities; these have been correlated. The magnitude of the hydrophobic attraction between ethyl xanthate treated galena particles, as determined from extrapolated yield data, has been shown to be greater at pH 5.5 than pH 10 and strongly concentration dependent. Rheological measurements of galena particle interactions are shown to enhance our understanding of fine pal-tide flotation and may be utilised to optimised flotation performance. (C) 1997 Elsevier Science B.V.